It is relatively common to perform ultrasonic examination of body parts of patients. Ultrasonic examinations are, of course, commonly carried out using an external ultrasonic probe in contact with the body part to be examined, that is, external to the body. The present invention is directed more particularly to endoscopic ultrasonic examination. As used herein, "endoscopic" ultrasonic examination refers to examination performed using a ultrasonic probe inserted through a portal in the patient's body, either a naturally occurring portal, such as the esophagus or rectum, or a surgically-formed portal.
In endoscopic ultrasonic imaging processes, a probe comprising a transducer head is inserted through an appropriate portal and manipulated so that the transducer head contacts the body part to be examined. The ultrasonic transducer is then energized by high-frequency signals passed to the transducer head via electrical conductors running down the length of the probe, such that pulses of ultrasonic energy are transmitted into the body part to be examined. The ultrasonic energy is reflected differentially from structures within the body part to be examined. The reflected energy is detected, typically by the same transducer, which then provides an electrical signal responsive to detection of the reflected energy. These signals can be processed according to generally known techniques to yield images of the body part to be examined.
It will be apparent that the transducer head must be properly aligned with respect to the body part to be imaged in order that a useful image can be formed. The prior art shows many structures for thus juxtaposing transducers of ultrasonic probes to body structures to be examined, and also shows various types of transducers and transducer head assemblies, including single-element and multiple-element transducer heads. The elements of multiple-element transducer heads are typically separately excitable in order to transmit ultrasonic energy in a specific pattern, and are operated so as to separately detect reflected energy.
Probes that are controllably articulable in specific bending planes in order to dispose the transducer head in a particular orientation with respect to a structure to be imaged are shown in a number of patents. For example, U.S. Pat. Nos. 5,170,787 to Lindegren, 5,158,086 to Brown et al, and 5,105,819 to Wollschlager et al disclose specific structures for articulated probes. The probe structures shown by these patents typically comprise a series of "vertebrae" extending along the length of an articulable portion of the probe. The vertebrae are pivotally joined to one another, such that their peripheries can be brought toward one another along a line extending along the outer edge of the articulable portion of the probe, while being spaced farther from one another along a diametrically opposed line. In this case, the probe bends in a plane including the two lines. Typically, the articulated section of the probe is operated by flexible tension members running parallel to the diametrically opposed lines, and controlled by a push-pull control arrangement, so as to simultaneously exert tension on one tension member, and release tension on the other. Hand-grippable knobs may be provided to allow a user to exert tension on one of the tension members while correspondingly releasing tension on the other. Such a structure, as used for an optical endoscope, is shown in U.S. Pat. No. 3,557,780 to Sato.
Articulable probe structures comprising vertebrae pivoted alternatingly to one another about orthogonal pivot axes are also known, for separately controllable articulation in orthogonal planes. In this case, two pairs of tension members and two push-pull control arrangements are provided, so as to provide separate articulation. Commonly, the push-pull control arrangements for such "four-way" articulated probes are operated by coaxial hand-grippable knobs; see U.S. Pat. Nos. 5,050,610 and 5,207,225 to Oaks et al.
In the Brown et al patent, generally cruciform vertebrae are joined by ball and socket snap-fit elements on the probe's axis, while four tension members are maintained at radially outward, circumferentially equally spaced positions by bearings formed on the cruciform portions of the vertebrae. Flexible electrical conductors communicating excitation signals to the ultrasonic transducer head and returning detected signals responsive to the detected ultrasonic energy are disposed between the cruciform portions of each of the vertebrae. The Brown et al patent further discloses motor-driven control of the tension members, such that rather than rotate a hand-grippable knob operating a push-pull mechanism to exert tension on one tension member of each pair while releasing tension on the other, the operator simply presses a button accomplishing the same end through the intermediary of an electric motor.
As indicated above, a number of different transducer head designs are shown in the prior art, providing a number of different ultrasonic energy emission patterns. Commonly, the transducer is "end firing"; that is, the transducer emits ultrasonic energy essentially from the end of the probe, such that the axis of the center of the probe is normally perpendicular to the structure of interest. Other references show transducers for performing a circular scan centered on the axis of elongation of the probe. See, for example, Matsui et al U.S. Pat. No. 5,099,850, disclosing a transducer rotated about the axis of the probe tip by a motor located in a handpiece and driving the transducer by a flexible cable extending along a lumen of the probe.
The prior art also shows further types of ultrasonic transducers and further transducer positioning arrangements. For example, U.S. Pat. Nos. 5,191,890 to Hileman and 5,215,092 to Wray appear to relate to the same system, and show a side-firing ultrasonic transducer mounted at the tip of an articulable section of the probe. See, e.g., FIGS. 3-5 of the Hileman patent.
Also of interest is U.S. Pat. No. 4,756,313 to Terwilliger showing a side-firing transducer separately pivotable about two orthogonal axes, both perpendicular to the axis of elongation of a rigid probe, so that a "fan-shaped" scan pattern can be oriented in various positions with respect to a structure to be imaged.
U.S. Pat. No. 5,199,437 to Langberg teaches a transducer having a helical scan pattern, this being stated to improve the image processing capabilities.
U.S. Pat. Nos. 4,834,102 and 4,977,898 to Schwarzchild et al show a miniature encapsulated ultrasonic transducer, having a scanning mechanism including a motor disposed in the tip of an ultrasonic transducer head.
U.S. Pat. Nos. 5,181,514 to Solomon et al and 5,176,142 to Mason relate to a system wherein a transducer array disposed at the end of a probe is rotated about an axis perpendicular to the axis of elongation of the probe by a motor located at a proximal end of the probe, so as to allow controllable alignment of the scanning plane. A position feedback device provides a signal indicative of the position of the transducer for analysis of the reflected ultrasonic energy in generation of an image.
A number of patents, including U.S. Pat. Nos. 4,869,263 to Segal et al, 4,771,788 to Millar, 4,757,818 to Angelsen, and 4,582,067 to Silverstein et al show Doppler blood flow sensors for disposition at the end of a probe. The Silverstein et al patent combines this with an articulable endoscope for providing a visible image of a body part. U.S. Pat. No. 4,462,408, also to Silverstein et al, teaches a flexible endoscope providing both visible and ultrasonic imaging capabilities.
U.S. Pat. No. 5,170,793 to Takano et al shows an ultrasonic probe wherein a mirror inclined at 45 degrees to the axis of elongation of the probe is continuously rotated by a flexible cable connected to a motor. The mirror is disposed opposite an ultrasonic transducer, such that as the mirror rotates a circular scan is effected. U.S. Pat. No. 4,489,727 to Matsuo et al shows a similar structure in an articulated probe.
The Oaks et al U.S. Pat. Nos. 5,207,225 and 5,050,610 teach an ultrasonic scan head for transesophageal use wherein a side-firing transducer emitting a "fan-shaped" beam can be rotated about an axis transverse to the tip of the probe. Compare FIGS. 2A and 2B of the Oaks et al '225 patent. The Oaks et al patents also teach, as mentioned above, that the probe can be separately articulated in orthogonal planes by operation of co-axial control knobs. The axis about which the transducer of Oaks et al rotates is fixed with respect to the planes of articulation of the probe. Assuming access is possible, such "four-way" articulation, together with the capability of rotating the entire probe about its axis of elongation, is sufficient to allow the side-firing transducer of Oaks to be juxtaposed to all sides of structures to be imaged. However, given that standard surgical procedures dictate use of certain portals only, it can be difficult using the Oaks et al and other known probes to form desired images of numerous body structures of interest. Moreover, having achieved a desired relation between the Oaks et al probe and the structure of interest, it is in many circumstances difficult to move the transducer head to another desired position.
More particularly, using a probe with a side-firing transducer array, that is, having an array of individual transducer elements extending along a line on the outer surface of the probe and parallel to its axis of elongation, it is difficult to mimic the scanning movements a physician uses when the probe is held in his or her hand, e.g., for external ultrasonic examination. It would be desirable to allow physicians to use the same motions for external and endoscopic examinations, as this would assist them in interpreting the images formed.
Physicians often use an external ultrasonic imaging technique wherein the image plane is perpendicular to the tissue surface, that is, extends into the body structure to be examined, while the probe is systematically moved over the surface, the probe motion being perpendicular to the scan plane. For example, a side-firing transducer may be moved along the abdomen of a pregnant woman, emitting a fan-shaped beam perpendicularly into the abdominal cavity. As the transducer is moved slowly perpendicular to the scan plane, a sequence of cross-sectional images is displayed.
A surgeon using a side-firing linear array transducer together with a four-way articulating probe might desire to make a similar sequence of images of the liver, that is, to see a sequence of cross-sectional images perpendicular to the surface of the organ. The surgeon may typically start by manipulating the probe such that the image plane is perpendicular to the plane of articulation, so that he can image perpendicularly to the tissue when the contact point is far removed from the portal. If he moves in a direction perpendicular to the image plane, that is, by articulating the probe, the probe end ultimately comes into contact with the tissue beneath the portal. If he has not readjusted the probe, the transducer will be firing parallel to the tissue and will not obtain an image. Accordingly, in order to obtain the proper orientation, the surgeon is required to change the plane of the articulation, e.g., by simultaneously operating two push-pull control arrangements, while also rotating the probe 90 degrees about its axis. Thus, the surgeon must simultaneously adjust three parameters to mimic a simple hand-held scan, and must do so without being able to observe the motion of the tip of the probe. This requires substantial coordination and is difficult for many practitioners to perform effectively.
Furthermore, the degree of linear movement provided is often limited. For example, a surgeon imaging the common bile duct using laparoscopic ultrasonic techniques eventually reaches a location where the transducer cannot be inserted any further. If the surgeon is using a rigid side-firing probe, he or she may then rotate the probe about its axis to obtain a series of angularly-spaced images, including structures somewhat beyond the point of linear motion. If the surgical portal does not allow placement of a straight probe into the appropriate spot for imaging the structure of interest, the surgeon must use an articulated probe to obtain the proper placement. However, using a conventional articulated probe precludes rotation of the probe to obtain angularly-spaced images, as above.
It can therefore be seen that despite the existence of substantial prior art directed to ultrasonic imaging probes, including probes which are articulable in one or two planes, and probes which include transducers rotatable about various axes to alter the scan orientation, there remain substantial deficiencies in the prior art.
The prior art also includes U. S. Pat. No. 4,696,544 to Costella, disclosing an articulable fiber optic device for optical inspection of the interiors of jet engine parts and the like. U.S. Pat. No. 4,688,554 to Habib shows a fiber-optic optical imaging endoscope slidably disposed within an articulated sleeve, in one embodiment including a bellows in the articulated section thereof. The endoscope forms an image directly opposite its tip. The sleeve is articulated to be bendable in a single direction. Thus, in order to juxtapose the imaging tip to a structure of interest, the sleeve is rotated to a desired angular position, defining a desired bending plane, and is then articulated. See Habib at col. 5, lines 52-63.
The prior art also includes a number of instruments for purposes other than ultrasonic imaging, wherein a variety of different motions are provided for implements at the tips of probes. For example, U.S. Pat. No. 5,254,130 to Poncet et al shows a surgical device wherein a cutting implement is disposed for rotation at the tip of a probe flexing responsive to a change in temperature of a shape memory element. U.S. Pat. No. 5,219,111 to Bilotti et al shows a surgical stapler comprising a stapling mechanism mounted on the end of an elongated shaft, the shaft being rotatable about its axis with respect to an actuating handle, and the stapling mechanism being pivotable about an axis normal to the shaft. See Col. 3, lines 19-24. A similar device is shown in U. S. Pat. No. 4,728,020 to Green et al. See also U.S. Pat. No. 4,566,620, also to Green et al, and showing further positional possibilities for a surgical stapler.